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Message-ID: <741b64c2-0b09-6475-5736-d2cd3e33c34c@arm.com>
Date: Tue, 13 Dec 2022 15:07:46 +0000
From: Robin Murphy <robin.murphy@....com>
To: Sibi Sankar <quic_sibis@...cinc.com>, andersson@...nel.org,
krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
manivannan.sadhasivam@...aro.org
Cc: agross@...nel.org, linux-arm-msm@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
konrad.dybcio@...ainline.org, amit.pundir@...aro.org,
regressions@...mhuis.info, sumit.semwal@...aro.org,
will@...nel.org, catalin.marinas@....com
Subject: Re: [PATCH 4/4] remoteproc: qcom_q6v5_mss: Use a carveout to
authenticate modem headers
On 2022-12-13 14:07, Sibi Sankar wrote:
> The memory region allocated using dma_alloc_attr with no kernel mapping
> attribute set would still be a part of the linear kernel map. Any access
> to this region by the application processor after assigning it to the
> remote Q6 will result in a XPU violation. Fix this by replacing the
> dynamically allocated memory region with a no-map carveout and unmap the
> modem metadata memory region before passing control to the remote Q6.
>
> Reported-by: Amit Pundir <amit.pundir@...aro.org>
> Fixes: 6c5a9dc2481b ("remoteproc: qcom: Make secure world call for mem ownership switch")
> Signed-off-by: Sibi Sankar <quic_sibis@...cinc.com>
> ---
>
> The addition of the carveout and memunmap is required only on SoCs that
> mandate memory protection before transferring control to Q6, hence the
> driver falls back to dynamic memory allocation in the absence of the
> modem metadata carveout.
The DMA_ATTR_NO_KERNEL_MAPPING stuff is still broken and pointless, so
I'd expect to see this solution replacing it, not being added alongside.
It's just silly to say pass the "I don't need a CPU mapping" flag, then
manually open-code the same CPU mapping you would have got if you
hadn't, in a way that only works at all when a cacheable alias exists
anyway.
Thanks,
Robin.
> drivers/remoteproc/qcom_q6v5_mss.c | 85 +++++++++++++++++++++---------
> 1 file changed, 61 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
> index fddb63cffee0..8264275ecbd0 100644
> --- a/drivers/remoteproc/qcom_q6v5_mss.c
> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> @@ -211,6 +211,7 @@ struct q6v5 {
> size_t mba_size;
> size_t dp_size;
>
> + phys_addr_t mdata_phys;
> phys_addr_t mpss_phys;
> phys_addr_t mpss_reloc;
> size_t mpss_size;
> @@ -935,6 +936,7 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
> {
> unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS | DMA_ATTR_NO_KERNEL_MAPPING;
> unsigned long flags = VM_DMA_COHERENT | VM_FLUSH_RESET_PERMS;
> + void *mdata_region;
> struct page **pages;
> struct page *page;
> dma_addr_t phys;
> @@ -951,34 +953,48 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
> if (IS_ERR(metadata))
> return PTR_ERR(metadata);
>
> - page = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
> - if (!page) {
> - kfree(metadata);
> - dev_err(qproc->dev, "failed to allocate mdt buffer\n");
> - return -ENOMEM;
> - }
> + if (qproc->mdata_phys) {
> + mdata_region = memremap(qproc->mdata_phys, size, MEMREMAP_WC);
> + if (!mdata_region) {
> + dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n",
> + &qproc->mdata_phys, size);
> + ret = -EBUSY;
> + goto free_dma_attrs;
> + }
>
> - count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> - pages = kmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
> - if (!pages) {
> - ret = -ENOMEM;
> - goto free_dma_attrs;
> - }
> + memcpy(mdata_region, metadata, size);
> + memunmap(mdata_region);
> + phys = qproc->mdata_phys;
> + } else {
> + page = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
> + if (!page) {
> + kfree(metadata);
> + dev_err(qproc->dev, "failed to allocate mdt buffer\n");
> + return -ENOMEM;
> + }
>
> - for (i = 0; i < count; i++)
> - pages[i] = nth_page(page, i);
> + count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> + pages = kmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
> + if (!pages) {
> + ret = -ENOMEM;
> + goto free_dma_attrs;
> + }
>
> - vaddr = vmap(pages, count, flags, pgprot_dmacoherent(PAGE_KERNEL));
> - kfree(pages);
> - if (!vaddr) {
> - dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n", &phys, size);
> - ret = -EBUSY;
> - goto free_dma_attrs;
> - }
> + for (i = 0; i < count; i++)
> + pages[i] = nth_page(page, i);
>
> - memcpy(vaddr, metadata, size);
> + vaddr = vmap(pages, count, flags, pgprot_dmacoherent(PAGE_KERNEL));
> + kfree(pages);
> + if (!vaddr) {
> + dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n", &phys, size);
> + ret = -EBUSY;
> + goto free_dma_attrs;
> + }
>
> - vunmap(vaddr);
> + memcpy(vaddr, metadata, size);
> +
> + vunmap(vaddr);
> + }
>
> /* Hypervisor mapping to access metadata by modem */
> mdata_perm = BIT(QCOM_SCM_VMID_HLOS);
> @@ -1008,7 +1024,8 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
> "mdt buffer not reclaimed system may become unstable\n");
>
> free_dma_attrs:
> - dma_free_attrs(qproc->dev, size, page, phys, dma_attrs);
> + if (!qproc->mdata_phys)
> + dma_free_attrs(qproc->dev, size, page, phys, dma_attrs);
> kfree(metadata);
>
> return ret < 0 ? ret : 0;
> @@ -1882,6 +1899,26 @@ static int q6v5_alloc_memory_region(struct q6v5 *qproc)
> qproc->mpss_phys = qproc->mpss_reloc = r.start;
> qproc->mpss_size = resource_size(&r);
>
> + if (!child) {
> + node = of_parse_phandle(qproc->dev->of_node, "memory-region", 2);
> + } else {
> + child = of_get_child_by_name(qproc->dev->of_node, "metadata");
> + node = of_parse_phandle(child, "memory-region", 0);
> + of_node_put(child);
> + }
> +
> + if (!node)
> + return 0;
> +
> + ret = of_address_to_resource(node, 0, &r);
> + of_node_put(node);
> + if (ret) {
> + dev_err(qproc->dev, "unable to resolve metadata region\n");
> + return ret;
> + }
> +
> + qproc->mdata_phys = r.start;
> +
> return 0;
> }
>
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